Review

A review of the mandibular and maxillary nerve suppliesand their clinical relevance

L.F. Rodella *, B. Buffoli, M. Labanca, R. Rezzani

Division of Human Anatomy, Department of Biomedical Sciences and Biotechnologies, University of Brescia, V.le Europa 11,

25123 Brescia, Italy

Contents

1. The trigeminal nerve: a general overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 324

1.1. Review methodology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 324

2. The mandibular nerve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 324

2.1. Anatomical variations of the mandibular nerve supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 324

2.1.1. Anatomical variations of the inferior alveolar nerve and its branches . . . . . . . . . . . . . . . . . . . . . . . . . 324

2.1.2. Anatomical variations of the lingual nerve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 328

2.1.3. Anatomical variations of the long buccal nerve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 329

2.1.4. Anatomical variation of the auriculotemporal nerve. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 329

2.1.5. Cervical plexus: additional innervation of the mandibular region . . . . . . . . . . . . . . . . . . . . . . . . . . . . 329

3. The maxillary nerve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 329

3.1. Anatomical variations of the maxillary nerve supply. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 329

3.1.1. Anatomical variations of the infraorbital nerve. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 330

3.1.2. Anatomical variations of the superior alveolar nerve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 330

a r c h i v e s o f o r a l b i o l o g y 5 7 ( 2 0 1 2 ) 3 2 3 – 3 3 4

a r t i c l e i n f o

Article history:

Accepted 20 September 2011

Keywords:

Mandibular nerve

Maxillary nerve

Anatomical variations

a b s t r a c t

Mandibular and maxillary nerve supplies are described in most anatomy textbooks.

Nevertheless, several anatomical variations can be found and some of them are clinically

relevant.

Several studies have described the anatomical variations of the branching pattern of the

trigeminal nerve in great detail. The aim of this review is to collect data from the literature

and gives a detailed description of the innervation of the mandible and maxilla.

We carried out a search of studies published in PubMed up to 2011, including clinical,

anatomical and radiological studies.

This paper gives an overview of the main anatomical variations of the maxillary and

mandibular nerve supplies, describing the anatomical variations that should be considered

by the clinicians to understand pathological situations better and to avoid complications

associated with anaesthesia and surgical procedures.

# 2011 Elsevier Ltd. All rights reserved.

* Corresponding author. Tel.: +39 0303717485; fax: +39 0303717486.

Available online at www.sciencedirect.com

journal homepage: http://www.elsevier.com/locate/aob

E-mail address: rodella@med.unibs.it (L.F. Rodella).

0003–9969/$ – see front matter # 2011 Elsevier Ltd. All rights reserved.doi:10.1016/j.archoralbio.2011.09.007

3.1.3. Anatomical variations of the palatine nerve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 331

3.1.4. Anatomical variations of the nasopalatine nerve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 332

4. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 332

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 332

a r c h i v e s o f o r a l b i o l o g y 5 7 ( 2 0 1 2 ) 3 2 3 – 3 3 4324

1. The trigeminal nerve: a general overview

The trigeminal nerve is the largest of the cranial nerves. It

originates from the brainstem at the midlateral surface of the

pons, near its upper border, by a smaller motor and a larger

sensory root. The afferent fibres transmit information from

the face, oral and nasal cavities, and most of the scalp. Most of

these fibres have their cell bodies located in the trigeminal

ganglion or Gasserian ganglion. With the exception of

periodontal ligament mechanoreceptors, the cell bodies of

the neurons involved in proprioception and the stretch

receptors are located in the mesencephalic nucleus. In

addition, the trigeminal nerve also contains visceral efferent

fibres for lacrimal, salivary and nasal mucosa glands; these

fibres come from facial and glossopharyngeal nerves and run

into the trigeminal nerve after an anastomosis with a branch

of the facial or glossopharyngeal nerves. Somatic efferent

fibres of the trigeminal nerve innervate the masticatory

muscles. They originate from the motor nucleus of the

trigeminal nerve located in the pons.

The trigeminal nerve gives three branches distal to the

trigeminal ganglion. The upper branch of the trigeminal nerve

is the ophthalmic nerve (V1). It passes forward in the lateral

wall of the cavernous sinus and gains access to the orbit via

the superior orbital fissure. The ophthalmic nerve gives

branches to supply sensation to the eyeball, conjunctiva,

lacrimal glands, nasal mucosa, skin of the nose, eyelid and

forehead. The middle branch is the maxillary nerve (V2).

Maxillary division exits the middle cranial fossa through the

foramen rotundum and enters into the pterygopalatine fossa

where it gives off several branches for the dura, the maxillary

teeth and associated gingiva, the maxillary sinus, the upper

lip, the lateral surface of the nose, the lower eyelid and

conjunctiva, the skin of the cheek and of the side of the

forehead, the nasal cavity and the mucosa of the hard and soft

palate. The lower branch is the mandibular nerve (V3). V3 runs

along the floor of the cranium then exits through the foramen

ovale into the infratemporal fossa and innervates the dura, the

temporomandibular joint, the skin over the side of the head

above the ears, the auricle, the tongue and its adjacent gingiva,

the muscle of the floor of the mouth, the mandibular teeth and

associated gingiva, the mucosa and skin of the cheek, the

lower lip and the chin and the muscles of mastication.

Given that the aim of this study is to describe the

anatomical variations of the branches of the trigeminal nerve,

which may have clinical implications during anaesthesia and

surgical procedures in dental and maxillofacial practice, we

have described the branching pattern of the mandibular and

the maxillary nerves in detail.

1.1. Review methodology

Literature about the anatomical variations of mandibular and

maxillary nerve was selected through a search of Medline,

PubMed and Google Scholar databases up to 2011. Additional-

ly, a manual search in the major anatomy, dental implant,

prosthetic and periodontal journal and books were performed.

The publications were selected by including clinical, anatomi-

cal and radiological studies.

2. The mandibular nerve

The mandibular nerve is the third and inferior division of the

trigeminal nerve. Unlike the ophthalmic and maxillary

divisions, which contain only afferent fibres, the mandibular

division contains both afferent and efferent fibres. It runs

from the trigeminal ganglion through the foramen ovale

down towards the mandible in the region of the infra-

temporal fossa giving off several branches. The main trunk

divides into the nervus spinosus, a recurrent meningeal

branch and the medial pterygoid nerve. Then, it divides into

a small anterior and a large posterior trunk; the masseteric

nerve, the deep temporal nerve, the long buccal nerve and

the lateral pterygoid nerve originate from the former; from

the posterior division the auriculotemporal nerve, the

lingual nerve and the inferior alveolar nerve originate.

The inferior alveolar nerve gives off the mylohyoid nerve

before it enters the mandible through the mandibular

foramen on the medial surface of the mandibular ramus

and gives two terminal branches: the mental nerve and the

incisive nerve.

2.1. Anatomical variations of the mandibular nervesupply

Variations in the branching pattern or topographical relations

of the mandibular nerve often account for failure to obtain

adequate local anaesthesia in routine oral and dental

procedures and for unexpected injury to branches of the

nerve during oral/maxillofacial surgery.1–5 To date, anatomi-

cal variations of the mandibular nerve and its branches have

been described by several authors.6–9

2.1.1. Anatomical variations of the inferior alveolar nerve andits branchesThe inferior alveolar nerve is the largest branch of the

mandibular nerve. It runs into the infratemporal fossa and

before entering the mandibular foramen originates a collateral

branch, the mylohyoid nerve for the innervation of the

mylohyoid and anterior belly of the digastric muscles. Then,

it enters the mandibular foramen and runs with the inferior

alveolar artery into the mandibular canal constituting the

inferior alveolar neurovascular bundle (Fig. 1). In the canal, the

nerve gives off two terminal branches: the mental nerve, a

larger branch that emerges from the mental foramen and

innervate the skin of the chin and the skin and the mucosa of

the lower lip and the incisive nerve, a smaller branch, which

Fig. 1 – Schematic representation of the mandibular nerve

and its branches. Some anatomical variations are

reported: (1) additional branches of the long buccal nerve;

(2) additional branches of the inferior alveolar nerve; (3)

communication between the mylohyoid nerve and the

lingual nerve; (4) communication between the inferior

alveolar nerve and the auriculotemporal nerve; (5)

innervation of the incisor teeth by the mylohyoid nerve; (6)

communication between the inferior alveolar nerve and

the lingual nerve. Nerves are shown in such a way as to

summarise optimally the main communication branches

of the mandibular nerve, although this may have resulted

in details of some of the nerve orientations being

modified.

Fig. 2 – Schematic representation of extraosseous multiple

branches of the inferior alveolar nerve showed after

osteotomy of the inner surface of the mandibula.

a r c h i v e s o f o r a l b i o l o g y 5 7 ( 2 0 1 2 ) 3 2 3 – 3 3 4 325

continues to travel in the mandible and provides sensory

innervation to the premolar, canine, incisor teeth and their

associated gingiva.

Here we have reported the following: the anatomical

variations of the inferior alveolar nerve compared to its

extraosseous and intraosseous branching pattern and its

relation with the maxillary artery, the anatomical variations of

the mental and incisive nerves and the anatomical variations

of the mylohyoid nerve.

2.1.1.1. Anatomical variations of the inferior alveolar ner-ve. The inferior alveolar nerve can give multiple (extraoss-

eous) branches before it enters the mandibular canal. Within

the bony canal it may give rise to multiple intraosseous

branches also. Throughout its course the inferior alveolar

nerve may support communicating branches with other

named parts of the mandibular division – such as the

mylohyoid nerve, the lingual nerve, the long buccal nerve

and the auriculotemporal nerve. All of these features will be

discussed in the relevant paragraphs. It may also show

anatomical variations in its relation with the maxillary artery.

2.1.1.1.1. The inferior alveolar nerve: extraosseous multiplebranches. The inferior alveolar nerve, before entering the

mandible, can give multiple branches. This variation is

associated with the presence of accessory foramina and

multiple canals so, understanding the mandible accessory

foramina can offers valuable insights into determining the

location of multiple branches (Figs. 1 and 2).

Several authors reported the presence of multiple forami-

na in the mandible and the important role of these accessory

foramina either in vascularisation or innervation has been

suggested.10–23 Supporting this concept, Nortje et al.24 found a

bifurcation of the nerve with bifid mandibular canals in 0.9%

(33/3612) of subjects, concluding that the mandibular canals

are usually, but not invariably, bilaterally symmetrical, and

most hemimandibles contain only one major canal. In

addition, Grover and Lorton25 performed a similar study

showing only 0.1% (4/5000) radiographs with this anomaly.

Furthermore, Langlais et al.15 evaluated routine panoramic

radiographs of 6000 patients and found 57 cases (0.95%) of

bifid mandibular canals, 19 in males and 38 in females.

Moreover, Sanchis et al.17 showed a prevalence of 0.35% from

the analysis of 2012 panoramic radiographs. Nevertheless,

Naitoh et al.26 by reconstructing 122 two-dimensional images

of the mandibular ramus region, observed bifid mandibular

canals in 65% of patients and classified it as retromolar,

dental, forward and buccolingual canals. De Oliveira-Santos

et al.27 also reported 19% of bifid mandibular canals using

cone beam computed tomography exams (CBCT). Cases of

trifid mandibular canal and bilateral bifid mandibular canal

were also described.20

Fig. 3 – Schematic representation of intraosseous multiple

branches of the inferior alveolar nerve showed after

osteotomy of the inner surface of the mandibula.

a r c h i v e s o f o r a l b i o l o g y 5 7 ( 2 0 1 2 ) 3 2 3 – 3 3 4326

Changes in the location of the mandibular foramen with

age should also be considered. Regarding this point, the

position of the mandibular foramen with age has been

described considering different landmarks. Kilarkaje et al.28

reported that the distance between the mandibular foramen

and different landmarks, (i.e., the head of the mandible, third

molar, anterior border of the ramus, angle of the mandible,

symphysis menti and lowest point on the mandibular notch),

gradually increased with advancing age. Moreover, compared

to the occlusal plane and the alveolar crest plane the

mandibular foramen was described moving upward with

age.29 For greater accuracy in anaesthetic procedures, dentists

should know the locational changes in the mandibular

foramen with age when performing block anaesthesia for

the inferior alveolar nerve.

The presence of accessory foramina was also associated

with the presence of additional branches of the inferior

alveolar nerve. In particular, branches of the inferior alveolar

nerve can be high in the infratemporal fossa and travel to the

base of the coronoid process to enter the mandible through

the retromolar foramina providing sensory innervation to the

molar teeth.14,30,31

These conditions can lead to complications when perform-

ing mandibular anaesthesia. In particular, since the bifurca-

tion occurs before the nerve enters the mandibular foramen, a

normal inferior alveolar nerve block may be insufficient to

block stimulus conduction for both branches, whilst alterna-

tive methods can be more effective.1,4

The common method for inferior alveolar anaesthesia is

the Halstead method, which has a success rate between 71%

and 87%.5,32 This approach is performed in the infratemporal

fossa, before the nerve enters the mandibular foramen.5 If the

Halstead method fails, alternative methods to block the

inferior alveolar nerve and the supplementary nerves that

could innervate the mandibular teeth could be used, e.g.,

buccal and lingual infiltrations, intraligamentary injection, the

Gow-Gates mandibular nerve block, the Vazirani-Akinosi

closed mouth mandibular block.33 In particular, the Vazir-

ani-Akinosi method can be useful when the patient cannot

open the mouth wide. In this case, in fact, the inferior alveolar

nerve is located far from the medial surface of the mandibular

ramus. On the contrary, the Gow-Gates method is performed

near the mandibular condyle, where the mandibular nerve is

not yet divided into its terminal branches.

Nevertheless, we should note that the presence of

accessory foramina could be related to the presence of blood

vessels only.4,24 This possibility could explain why the

presence of accessory mandibular canals and foramina based

on panoramic radiographs is not always associated with

difficulty in obtaining mandibular anaesthesia.

2.1.1.1.2. Variations in the intraosseous course of the inferioralveolar nerve. Even if the inferior alveolar nerve enters the

mandible by a single foramen, it can have several variations

during its course into the mandibular canal.34

(1) The nerve can enter the mandibular foramen and run into

the mandibular canal as a single trunk giving branches for

molar and premolar teeth. In the premolar region, the

nerve gives the incisive nerve for premolar, canine and

incisor teeth and the mental nerve.

(2) The nerve can give a major and minor trunk near the

mandibular foramen; the major trunk runs into the

mandibular canal and emerges from mental foramen,

whereas the minor trunk (dental ramus) innervates molar

and premolar teeth and then becomes the incisive nerve

(Fig. 3).

(3) The nerve gives three branches near the mandibular

foramen for molar and premolar teeth, for canine and

incisor teeth and for mental foramen.

2.1.1.1.3. Relation between the inferior alveolar nerve and themaxillary artery. The maxillary artery is the larger terminal

branch of the external carotid artery arises in the parotid gland

behind the neck of the mandible and crosses the infratem-

poral fossa to enter the pterygopalatine fossa through the

pterygomaxillary fissure. It crosses the inferior alveolar nerve

and the lingual nerve and runs along the lower border of the

lateral pterygoid muscle.

Unusual variations in the relation between the inferior

alveolar nerve and the maxillary artery, have been observed by

several authors.7,35,36 Roy et al.7 reported that, in one specimen

of 40 human heads analysed, the inferior alveolar nerve

originated from the posterior division of the mandibular nerve

by two distinct roots, without any communication with other

branches of the mandibular nerve. These branches joined to

form a single trunk and incorporated between them the

second part of the maxillary artery. Recently, Khan et al.37

found a similar pattern in the second part of the maxillary

artery which passed through the inferior alveolar nerve,

splitting the nerve into superficial and deep divisions, which

rejoined inferior to the maxillary artery. There was an

additional case in which the inferior alveolar nerve had three

roots and the maxillary artery passed between two of them.38

Moreover, other anatomical variations concerning the

relation between the inferior alveolar nerve, the maxillary

artery and other surrounding structures have also been

reported. Anil et al.3 examining 20 dissections of the

a r c h i v e s o f o r a l b i o l o g y 5 7 ( 2 0 1 2 ) 3 2 3 – 3 3 4 327

infratemporal fossa, found in two specimens that the

maxillary artery was entrapped within a loop formed by the

root of the inferior alveolar nerve and a connecting nerve

branch originating from the auriculotemporal nerve versus

the inferior alveolar nerve. Moreover, an unusual relation

where the maxillary artery was located between the inferior

alveolar nerve and the lingual nerve has been described

recently.39

In addition, the maxillary artery was reported to pierce only

the lingual nerve or a common trunk formed by the inferior

alveolar nerve and the lingual nerve.40

These anatomical relations could explain certain trigemi-

nal pain conditions and must be considered for dental,

oncological, reconstructive surgery of the infratemporal fossa

and for adequate anaesthesia.7 The vascular compression of

the afferent fibres of the inferior alveolar nerve by the

pulsating maxillary artery may cause pain and numbness

without any neurological symptoms. Moreover, sensory

alterations could be caused by intravascular puncture of the

maxillary artery following local anaesthetic; the procedure

can cause a haematoma that exerts soft pressure on the closed

anatomical structures.

2.1.1.2. Anatomical variations of the mental nerve. The mental

nerve is one of the terminal branches of the inferior alveolar

nerve. It emerges through the mental foramen and branches

out into three parts; one of them descends to the skin of the

chin and the other two ascend to the skin and mucosa of the

lower lip. The mental foramen lies below the level of premolar

teeth. The location and emergence of this nerve have been

described in several studies and their changes in relation with

aged and the teeth presence was also reported.41,42

2.1.1.2.1. Additional branches of the mental nerve andaccessory mental foramina. Contradictory data concerning

the presence of accessory mental foramen have also been

reported. Some authors report that accessory foramen is

located apical or proximal to the mental foramen and contains

mental nerve fibres. Shankland43 reported a 6.62% prevalence

of accessory mental foramina, Parameswaran and Udayaku-

mar44 recorded a considerably smaller percentage (2.5%) and

Grover and Lorton25 found no accessory foramina in series of

5000 panoramic X-rays. A higher percentage was recently

reported by Naitoh et al.45 by using CBCT. Moreover, the

presence of accessory mental foramen located in the lingual

cortical bone of the mandible46 and a case of triple mental

foramina has recently been describe.47

The presence of accessory foramina can be associated with

additional branches of the mental nerve. A rare case of two

mental nerves emerging from two different mental foramina

has been reported reported48,49: the two nerves were almost the

same diameter and the accessory mental foramen was located

adjacent to each other on the same side of the mandible.

The oral and maxillofacial surgeon should consider the

importance of adequate preoperative radiological examina-

tion and should be careful during surgical procedures, in

surgery below the second premolar tooth, to prevent possible

nerve damage.

2.1.1.2.2. Different pattern of emergence of the mentalnerve. Whilst the emphasis of some research has been on

the exact positioning of the mental foramen, a number of

studies have addressed the path of emergence of the mental

neurovascular bundle.41,42,50

Serman51,52 produced evidence for a mental foramen

complex in which the nerve re-enters the mandible through

a more anterior foramen after a short extraosseous course.

This hypothesis was supported by Pogrel et al.,53 who

suggested a crossover innervation of incisors from the

contralateral mental nerve.

Some investigators described an anterior loop to the nerve

before its emergence from the mental foramen. The existence

of this loop was challenged by Rosenquist.54 Support for this

study was given by Kieser et al.55 who reported that the mental

nerve most frequently emerges in a posterior orientation and

that the most common patterns of emergence observed were

either a Y- or T-shaped divergence between the mental and

incisive nerves, with non-distinct anterior loops.

The reason for this is unclear, but it is argued that the

change in the orientation could be ascribed to forward growth

of the mandible, which dragged the neurovascular bundle

along with it.56 Warwick57 first suggested that the posterior

inclination of the foramen was related to the development of

the human chin. This view was supported by Montagu42 who

suggested that the gradient of the growth of the mandible was

directed posteriorly and hence, the foramen could be expected

to open in the same direction. In addition, the work of De

Villiers58 offered empirical support showing that the mental

foramen emerged with an anterior inclination in the cases of

unerupted first deciduous molars.

Interest in the emergence and location of the mental nerve

has been rekindled by the need for accurate pre-operative

surgical planning for the placement of mandibular implants

and for all surgical procedures that need osteotomy near the

mental nerve emergence.

2.1.1.2.3. Cross innervation of the incisor teeth by thecontralateral mental nerve. Some evidence suggest that

branches of the mental nerve could cross the midline and

re-enter in the mandible through accessory foramen providing

innervation to the contralateral incisor teeth.51,53 This varia-

tion should be considered for anaesthetic procedures. Indeed,

in this situation, the Halstead method, i.e., the mental nerve

block and the infiltration near the tooth apex could not provide

adequate anaesthesia and supplementary injections, such as

bilateral inferior alveolar or mental nerve block, or a labial

infiltration, may be necessary.

2.1.1.3. Anatomical variations of the incisive nerve. The inci-

sive nerve is one of the terminal branches of the inferior

alveolar nerve. It continues within a bone canal or constitutes

the incisive plexus providing the innervation to the premolar,

canine, incisor teeth and their associated gingiva.

2.1.1.3.1. Cross innervation of the incisor teeth by the

contralateral incisive nerve. It is widely accepted that the

incisive nerve is extensively branched and also innervates

the contralateral side.59 This variation was demonstrated by

mapping an area of anaesthesia after the inferior alveolar

block: in 8 on 19 cases. Stewart and Wilson60 noted that the

midline of the body may not correspond exactly with the

midline for the nerve. On the contrary, other authors did not

observe this variation and found that the incisive nerve did not

cross the midline.10,61

a r c h i v e s o f o r a l b i o l o g y 5 7 ( 2 0 1 2 ) 3 2 3 – 3 3 4328

The reason for this could be ascribed to the origin of the

mandible, which is formed by the fusion of the bilateral first

pharyngeal arches, creating the possibility of crossover

innervation.

2.1.1.4. Anatomical variations of the mylohyoid nerve. The

mylohyoid nerve originates from a small posterior branch of

the inferior alveolar nerve before the latter enters the

mandibular foramen (Fig. 1). It originates at variable

distances superior to the mandibular foramen.62,63 After

branching from the inferior alveolar nerve, the mylohyoid

nerve courses downward and anteriorly within mylohyoid

groove on the medial surface of the mandible providing

innervation to the mylohyoid and the anterior belly of the

digastric muscles. Nevertheless, some fibres could enter the

mandibular through the retromandibular foramina and

provide innervation to premolar, canine and incisor

teeth.5,13,33,63–65

2.1.1.4.1. Additional innervation of the mandibular teeth bythe mylohyoid nerve. The anatomy of the mylohyoid nerve is

variable in relation to its level of branching, course through the

mylohyoid groove, branch numbers to the mylohyoid and

digastric muscles and terminal branching in the submental

region.

Numerous studies indicate the mylohyoid nerve as an

alternate ‘‘escape route’’ for pain in the mandibular

teeth.5,12,62,65–67 In particular, the presence of accessory

mandibular foramina explains the potential innervation of

the mandibular teeth by the mylohyoid nerve.

Some authors5,62,65,67 described the presence of mylohyoid

branches into the mandible by entering the retromental

foramina, which are accessory foramina (superior and inferi-

or) that occur on the lingual surface of the mandible in an area

superior to the genial tubercles and at the inferior border of the

mandible. In addition, intraosseous dissections of the mylo-

hyoid nerve shows that its branches could terminate directly

in the incisor teeth or connecting with the ipsilateral or

contralateral incisive nerve (Fig. 1).62,65 Moreover, Carter and

Keen found that the mandibular teeth are innervated by a

nervous plexus constituted by the mylohyoid nerve and the

dental branch of the inferior alveolar nerve.12 The mixed

nature of the mylohyoid nerve was confirmed by a study that

described the presence of both Ad fibres (afferent) and Aa

fibres (efferent) in this nerve.68

An important factor related to the additional sensitive

branches of the mylohyoid nerve fibres is the presence of the

teeth. Indeed, the number of fibres is reported to decrease in

edentulous patients, reinforcing the idea that the mylohyoid

nerve is involved in the teeth innervation.69,70

Regarding the clinical implications of the teeth innerva-

tion by the mylohyoid nerve, it could be explained by

incomplete anaesthesia during routine oral and dental

procedures.5,71 In addition, the surgeons must be aware of

this variation for a correct interpretation of unexpected

findings after oral nerve injury. The administration of

anaesthetic solution near the mandibular foramen may have

effect only on the inferior alveolar nerve. Therefore, to

provide adequate anaesthesia to mandibular teeth, the

mylohyoid nerve block performed near the retromental

foramina is recommended.

2.1.2. Anatomical variations of the lingual nerveThe lingual nerve is a terminal branch of the posterior division

of the mandibular nerve. It enters the mouth between the

medial pterygoid muscle and the ramus of mandible and then

passes anteriorly under cover of the oral mucosa, just inferior

to the third molar tooth. It is a sensory nerve to the anterior

two-thirds of the tongue, the floor of the mouth and lingual

gingiva. Moreover, it contains parasympathetic fibres from the

facial nerve for the sublingual and submandibular glands.

The lingual nerve runs anterior to the inferior alveolar

nerve, so it is often anesthetised during inferior alveolar nerve

block. Moreover, because of its anatomical location, lingual

nerve injury is possible during oral surgery, such as third

molar extraction, mandibular trauma management, periodon-

tal procedures and excision of neoplastic lesions.72,73

2.1.2.1. Relation of the lingual nerve with the third molar

region. A significant complication of third molar removal is

lingual nerve injury. Some data has reported that the

frequency of lingual nerve injuries during oral and maxillofa-

cial procedures varies between 0.6% and 2%.74–76 These

injuries often result in anaesthesia, paresthesia or hypesthe-

sia of the anterior part of the tongue and it can affected taste.

However, permanent damage to the nerve is uncommon77 and

there is little detailed data on the spontaneous recovery

rate.78–80

Consequently, the precise anatomical knowledge of its

location in the third molar region plays an important role in

planning and performing surgical procedures in this area.81

Cadaveric dissections, clinical and radiographic observations

could provide useful information to localize this nerve. In

particular, the mean values of the distance of the lingual nerve

to the lingual plate and crest in the third molar region could be

an useful index during surgical procedures and help the

maxillofacial surgeon to prevent lingual nerve damage.75,82–84

Quantitative studies on the position of the lingual nerve in the

third molar region report that the mean horizontal distance of

the nerve from the lingual plate ranges from 0.58 mm to

3.45 mm, whereas the mean vertical distance of the lingual

nerve below the alveolar crest is between was 2.28 mm and

8.32 mm.82,83 Some years later, Karakas et al.75 found similar

data and reported that the mean vertical and horizontal

distances of the nerve to the lingual crest and lingual plate of

the mandible were 9.5 � 5.2 mm and 4.1 � 1.9 mm respective-

ly. Discrepancies in measurement data could be related to

race, genetic and individual constitution. On the other hand,

the presence or absence of teeth in the retromolar area and the

loss of muscle tone and connective tissue tension with

advancing age has no statistical relation to the nerves position

or relation to the crest of the lingual plate.83,85

2.1.2.2. Communication between the inferior alveolar nerve andthe lingual nerve. The communication between the inferior

alveolar nerve and the lingual nerve has been described by

several authors (Fig. 1). Racz et al.6 in a study of lingual nerve

made in 48 half-heads of 24 cadavers, found communication

between the lingual nerve and the inferior alveolar nerve in

25% of cases. This finding was also reported by Khaledpour86

but with an incidence of about 7%. More recently, during the

dissection of 24 head halves of 12 Japanese cadavers, a

a r c h i v e s o f o r a l b i o l o g y 5 7 ( 2 0 1 2 ) 3 2 3 – 3 3 4 329

communicating branch between these two nerves was

frequently observed proximal to the originating point of the

mylohyoid nerve.87

The communication between the two nerves suggests: (1)

the contribution of the afferent and parasympathetic fibres

from the lingual nerve to the inferior alveolar nerve

respectively for supplementary innervation to the teeth and

the innervation of the lower labial salivary glands; (2) the

contribution of afferent fibres from the inferior alveolar nerve

for the regions innervated by the lingual nerve.

This supplementary innervation must be considered

during the anaesthesia.

2.1.2.3. Communication between the mylohyoid and the lingualnerve. A communicating branch between the mylohyoid and

lingual nerve has been reported. In particular, branches of the

mylohyoid nerve could contribute to the sensory innervation

of the tongue by the presence of anastomosis between this

nerve and the lingual nerve (Fig. 1).

Racz et al.6 studying 48 human half-heads, described a

communication branch between the mylohyoid nerve and the

lingual nerve in 33% of examined cases. More recently, Kim

et al.73 described communication between the mylohyoid and

the lingual nerve in 12.5% of examined cases and they first

mentioned that this communication could provide another

route for collateral sensory transmission to the tongue. Sassoli

Fazan et al.88 reinforced this idea, indicating that some of the

afferent fibres of the mylohyoid nerve might also innervate the

tongue.

The anastomosis between the mylohyoid and the lingual

nerves was found to occur after that the lingual nerve passes

close to the third molar region, making it susceptible to injury

during the third molar extraction.89 Moreover, the presence of

a communication between the mylohyoid and the lingual

nerves could help in lingual nerve function recovery after third

molar removal, since the mylohyoid nerve could be contrib-

uting to the sensory innervation of the tongue.88,89

2.1.2.4. Collateral branches from the lingual nerve. Lingual

nerve has often several additional branches. Kim et al.73

reported that collateral nerve branches originated from the

lingual nerve and innervated the lingual gingiva around the

lower third molar and the retromolar region. These were

observed in 81.2% of examined cases, indicating that this

anatomical variation could be considered a normal innerva-

tion pattern variation, as previously suggested by other

works.90,91 This collateral innervation may explain the

incomplete anaesthesia during the mandibular nerve block

anaesthetic procedure.

2.1.3. Anatomical variations of the long buccal nerveThe long buccal nerve, a branch of the mandibular division of

the trigeminal nerve, arises quite high in the infratemporal

fossa, runs between the two heads of the lateral pterygoid

muscle and then descends in a forward direction in associa-

tion with the maxillary artery and medial to the tendon of the

temporalis muscle and Bichat’s fat pad. It connects with

the buccal branch of the facial nerve and reaches the skin over

the buccinator muscle. The long buccal nerve also carries

afferent fibres to the lower buccal gingiva, lower buccal sulcus

and the mucosa of the cheek and may contribute to the

extraoral cutaneous supply of the cheek.

2.1.3.1. Additional innervation of the teeth by the long buccalnerve. The innervation of the molar teeth could be ascribed to

the long buccal nerve, a branch of the anterior division of the

mandibular nerve.4,92 Indeed, branches of this nerve could

enter in the retromolar foramina (Fig. 1).33 This variation could

be responsible for the failure of the traditional inferior alveolar

nerve block.4,31,93

2.1.4. Anatomical variation of the auriculotemporal nerveThe auriculotemporal nerve runs medial to lateral behind the

neck of the mandible, gives off parotid branches and then

turns superiorly, posterior to its head and moving anteriorly,

giving off anterior branches to the auricle. Then, it crosses over

the root of the zygomatic process of the temporal bone, deep to

the superficial temporal artery. In literature, some cases of a

connection between the auriculotemporal nerve and the

inferior alveolar nerve have been described (Fig. 1).3,6,8,86

Variations in the anatomy of the auriculotemporal nerve

are of great interest for regional anaesthesia.94,95 Indeed,

anastomosis between the fibres of the auriculotemporal nerve

and the inferior alveolar nerve could compromise the efficacy

of the inferior alveolar nerve block.

2.1.5. Cervical plexus: additional innervation of themandibular regionBranches of the cervical plexus could provide additional

innervation of the mandibular region. The great auricular

nerve arises from the cervical plexus and provides sensory

innervation of the skin over the parotid gland, the mastoid

process and the outer ears. In particular, the anaesthesia of the

great auricular nerve that arises from the cervical plexus was

reported in a case of third molar extraction when conventional

anaesthesia failed, suggesting an involvement of great

auricular nerve in the innervation of the angle of the mandible

(Fig. 4).96 Consequently, a separate infiltration may be needed

to achieve total analgesia of the mandibular region.

3. The maxillary nerve

The maxillary nerve is a sensory nerve. After its origin from

the trigeminal ganglion, the maxillary nerve passes through

the cavernous sinus below the ophthalmic nerve, exits

through the foramen rotundum and enters into the pterygo-

palatine fossa. In the fossa, several sensory branches are given

off the meningeal branches, the superior alveolar nerves, the

zygomatic and infraorbital nerves. The other branches

originate from the pterygopalatine ganglion: the nasal and

palatine nerves.

3.1. Anatomical variations of the maxillary nerve supply

Detailed knowledge of the anatomical variations of the

maxillary nerve is necessary for a surgeon whilst performing

maxillofacial surgery and regional block anaesthesia. In the

literature, there is little data concerning the maxillary nerve

component. Siessere et al.9 dissected 20 human heads to study

Fig. 4 – Schematic representation of the great auricular nerve from the cervical plexus. ***Branch supplying the innervation

to the angle of the mandible.

a r c h i v e s o f o r a l b i o l o g y 5 7 ( 2 0 1 2 ) 3 2 3 – 3 3 4330

their structures from an external, medial and endocranial

view and they observed no significant variations relating to the

ophthalmic and maxillary nerves. On the contrary, anatomical

variations were found in 20% of cases in relation with the

mandibular nerve and its branches.

3.1.1. Anatomical variations of the infraorbital nerveThe infraorbital nerve is a direct extension of the maxillary

division of the trigeminal nerve (Fig. 5). It courses anteriorly

through a canal within the bone of the orbital floor and

provides superior alveolar nerves for the sensory innervation

Fig. 5 – Schematic representation of the maxillary nerve

and its branches. ***Dental plexus.

of the maxillary teeth. The infraorbital nerve then emerges

from the infraorbital foramen and gives 4 branches, the

inferior palpebral, the external nasal, the internal nasal and

the superior labial branches for the sensory innervation to the

skin of the eyelid, nose, cheek and upper lip.

The infraorbital foramen is usually (90–97%) single never-

theless, several studies have underlined the presence of two or

three foramina.97–103 Aziz et al.99 reported a 15% incidence of

accessory infraorbital foramina. A low percentage (4.7%) was

observed during a study on 1064 skulls, with a higher

frequency on the left side, both in male and in female

skulls.101 In addition, an incidence of 1.3% was found by

Gupta.102 Moreover, a case of bifid foramina associated with a

bifid infraorbital nerve was found during a cadaver dissection

of a 69-year old man.103 Normally, the distance from the

infraorbital foramen to the inferior border of the orbital rim is

from 4.6 to 10.4 mm99,100,104,105 depending on the landmarks

chosen for measurements.

Since the infraorbital nerve block is often used to achieve

regional anaesthesia of the face, the study of frequency and

position of accessory infraorbital foramen are useful to reduce

anaesthetic and surgical complications, especially in trunk

block of the infraorbital nerve.

3.1.2. Anatomical variations of the superior alveolar nerveThe superior alveolar nerve is given off from the maxillary

nerve in the pterygopalatine fossa, runs in the infraorbital

canal and divides into branches, which supply the maxillary

teeth. Traditionally, researchers and clinicians have under-

stood that there are three alveolar nerves: the anterior, middle

and posterior superior alveolar nerves that carry sensation to

the maxillary teeth; nevertheless, the middle superior alveolar

nerve could be absent, consequently it is often considered an

anatomical variant.

a r c h i v e s o f o r a l b i o l o g y 5 7 ( 2 0 1 2 ) 3 2 3 – 3 3 4 331

The contribution of the three alveolar nerves to the

maxillary teeth innervation has been reported being different.

The superior molar teeth are normally innervated from the

posterior superior alveolar nerve and occasionally from the

middle superior alveolar nerve, whereas there is no innerva-

tion to the first molar from the anterior superior alveolar

nerve.106,107 Regarding the superior premolar teeth, it is

interesting to observe that some patients have only two

maxillary alveolar nerves and that the middle superior

alveolar nerve, the innervation ascribes to the premolar teeth

was often missing107,108 and was provided by the posterior

superior alveolar nerve. The innervation of the canine and

incisor teeth is normally due to anterior superior alveolar

nerve; nevertheless, Robinson and Wormald109 showed that

there was a wide variation to the branching pattern of the

anterior superior alveolar nerve and the middle superior

alveolar nerve within the anterior face of the maxilla.

Unfortunately, there are no anatomical predictors of the

innervation pattern. Therefore, clinicians may have to modify

their approach to avoid anaesthetic procedure failure.

3.1.2.1. The posterior superior alveolar nerve. The posterior

superior alveolar nerve originates from the maxillary nerve

just before it enters the infraorbital groove (Fig. 5). It descends

on the tuberosity of the maxilla and gives off several branches

to the gingival and the mucosa of the cheek. Then it enters

the posterior alveolar canal on the infratemporal surface of

the maxilla and gives off branches to the membrane of the

maxillary sinus and the molar teeth. Several variations in the

branching pattern of this nerve have been reported; in

particular, it could be found as a single or a multiple nerve

branches.

McDaniel110 found that the posterior superior alveolar

nerve had one branch in 21%, two branches in 30% and three

branches in 25% of specimens. Where multiple branches were

present, the branches entered the highest foramen and

supplied the anterior teeth.

Even if the branching pattern of this nerve should be

considered during anaesthetic procedures in this region, the

different origins of the posterior superior alveolar nerve

compared to the middle and the anterior branches offers

the possibility to anesthetise only the posterior branch.

Indeed, the posterior superior alveolar nerve is approached

near the maxillary tuberosity, whereas the anterior superior

alveolar nerve in the region of infraorbital foramen.

Moreover, occasionally, the posterior superior alveolar

nerve block may not cause complete maxillary molar

anaesthesia due to the presence of branches from the palatine

nerve that could innervate the molar and premolar teeth.33 In

this case, the greater palatine nerve block could be associated

to the posterior superior alveolar nerve block to enhance the

anaesthetic effects. Alternative to the greater palatine nerve

block could be plexus anaesthetic injection on the palatal

aspect.

3.1.2.2. The middle superior alveolar nerve. The middle super-

ior alveolar nerve is given off from the infraorbital nerve,

during its course in the infraorbital canal, and runs in the

lateral wall of the maxillary sinus to supply the premolar

teeth (Fig. 5).

McDaniel110 reported that the middle superior alveolar

nerve followed the classical description in only 30% of

examined cases whilst the majority of middle branch entered

the formation of a nerve plexus that supplied the teeth. When

the middle branch was absent, the innervation of the premolar

teeth may be provided by secondary branches of the anterior

superior alveolar nerve, by the posterior superior alveolar

nerve or by a nervous plexus between these two nerves. Even if

this situation is not easily detectable, this variation should be

considered during anaesthetic procedures.

3.1.2.3. The anterior superior alveolar nerve. The anterior

superior alveolar nerve comes from the infraorbital nerve at

variable distances from the infraorbital foramen. The nerve

arises from the middle and anterior thirds of the infraorbital

nerve and courses in the infraorbital canal. After entering the

anterior face of the maxilla, it courses across the maxilla

towards the canine fossa before branching and forming the

superior dental plexus located in the maxillary alveolar

process (Fig. 5). The anterior superior alveolar nerve was

present as a single trunk in 75%, of cases as reported by

McDaniel110; in 35% there was a diffuse fine plexus of the

anterior superior alveolar nerve branches overlying the canine

fossa. The presence of a superior dental plexus appears to be

favoured by multiple posterior branches and by the presence

of a middle branch or an anterior branch with multiple main

branches.

It is important to monitor facial sensation preoperatively

and to carefully identify the nerve course during preoperative

radiologic evaluation because injury to it may have implica-

tions on the patient’s quality of life post-operatively. Trau-

matic or iatrogenic injury to this nerve may result in

hypesthesia, paresthesia, or pain in this area. Computed

tomography with triplanar reconstruction has enhanced our

ability to delineate the course of the infraorbital nerve through

its bony canal.

3.1.3. Anatomical variations of the palatine nerve

The greater palatine nerve is the anterior branch of the

palatine nerve; it runs in the inferior area of the hard palate

and innervates the palatal gingiva and the hard palate. The

palatine nerve is distributed to the roof of the mouth, soft

palate, tonsil, and lining membrane of the nasal cavity. Most of

its fibres derive from the sphenopalatine branch of the

maxillary nerve. In older textbooks, it is usually categorized

as anterior, middle, and posterior palatine nerve. More recent

textbooks simplify the distribution into the greater palatine

nerve and the lesser palatine nerve.

Variations of the location of greater palatine foramen have

been reported.111,112 The first description of the location of the

greater palatine foramen was reported by Matsuda.113 In

particular, it was opposite the maxillary second or third

molar114 or anywhere between the maxillary second and third

molar.115 A recent study112 confirmed the presence of the

foramen opposite the maxillary third molar (54.87%) distal to

the maxillary third molar (38.94%) and between the maxillary

second and third molar (6.19%).

Variations were also described for nerve supply; indeed, the

greater palatine nerve can sometimes gives additional

branches for the molar and premolar maxillary teeth. This

a r c h i v e s o f o r a l b i o l o g y 5 7 ( 2 0 1 2 ) 3 2 3 – 3 3 4332

variation has to be considered for a complete and adequate

superior alveolar nerve block.

3.1.4. Anatomical variations of the nasopalatine nerve

The nasopalatine nerve is a branch of the sphenopalatine

nerve; it enters the nasal cavity through the sphenopalatine

foramen, passes across the roof of the nasal cavity and runs

obliquely downward and forward; it descends to the roof of the

mouth through the incisive canal and it emerges from the

nasopalatine foramen. Anatomical variations of this nerve are

related to the pattern of innervation. It usually provides

innervation to the palate and palatal gingiva near the canine

teeth. Nevertheless, in some cases it could give some branches

for the innervation of the incisor teeth.116 Consequently, the

nasopalatine nerve block should be necessary to completely

anesthetise the central incisor.

4. Conclusion

This review summarises data in the literature concerning

anatomical variations of mandibular and maxillary nerve

supplies in order to provide an update of the main anatomical

variations concerning these nerves and consequently, to give

detailed anatomical basis for a better understanding of clinical

and surgical practice related to oral and maxillofacial area.

The knowledge of the branching patterns of the trigeminal

nerve, the additional innervation and the presence of

accessory canals and foramina should be carefully considered

for choosing the best plan and consequently for optimizing

anaesthetic and surgery procedure during oral and maxillofa-

cial procedures.

Funding

Local institutional grant.

Competing interest

None.

Ethical approval

None.

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